Gripper assemblies are used for handling and transporting parts, often in conjunction with automated pneumatically powered robotics type machinery. Examples of prior attempts at gripper assemblies are illustrated in Borcea et al., U.S. Pat. No. 4,667,998 and Borcea et al., U.S. Pat. No. 4,593,948. As is typical, the gripper assembly includes a housing and a plurality of arms (typically two or three arms) that are movable towards and away from each other relative to the body. The arms are typically either pivotably connected to the housing for pivoting movement about a pivot axis or slidably mounted for linear reciprocation towards and away from each other. An actuating mechanism, usually in the form of a pneumatically powered piston, is mounted in the housing for reciprocating the arms towards and away from each other.
Gripper assemblies are off-shelf-components that are selected for use in a wide range of machine applications. Gripper assemblies are preferably compact so to prevent interference with other moving parts in a working machine incorporating the gripper assembly. It is often desirable to perform work on the workpiece while the workpiece is being held between the arms of a gripper assembly. One problem with prior gripper assemblies in certain applications is that there is not a highly reliable method for determining whether a part is held and/or properly held by a gripper assembly. Yet another problem with prior gripper assemblies is that it has been relatively difficult to perform certain work on a workpiece held by a gripper assembly. It may be necessary to configure the machine utilizing the gripper assembly in a less desirable and/or more costly manner to accomplish the desired work.